The present invention relates generally to radio frequency shield enclosures, and more particularly to a radio frequency shield enclosure mounted onto a printed circuit board and having a removable cover.
Radio frequency shielding, e.g., shielding chambers or enclosures, in electronic equipment such as mobile telephones is necessary in order to reduce receiver radio frequency interference from digital circuit switching noise and malfunction of the digital circuits from locally transmitted radio frequency signals. In addition, shielding may be required for circuit protection from externally generated radio frequency and electromagnetic interference. These shielding chambers may be formed by a frame soldered on a printed circuit board and a mechanically attached cover (lid).
Typically, the frame is placed onto the printed circuit board along with the electronic components using standard SMD pick-and-place technology equipment on the production line before the printed circuit board goes through re-flow soldering. Then optical inspection is performed to ensure proper placement of the components. After passing the optical inspection, a functional electrical test is performed on the printed circuit board. If the functional electrical test is passed, then a separate shield cover is mechanically placed onto the frame.
Having to mechanically assemble the cover onto the frame after re-flow soldering and testing may cause bending of the printed circuit board that may result in excessive stresses thereto. These stresses may damage the printed circuit board conductors, connections and/or components thereon, leading to premature failure of the product. There may also be a problem with signal leakage during the testing phase because the shield cover has not yet been placed onto the frame.
What is needed is a shielding chamber that does not create unnecessary stress on the printed circuit board during assembly and testing, allows optical inspection of components placed onto the printed circuit board, can be easily opened for reworking of the printed circuit board if problems are found during testing, may be easily closed up to maintain radio frequency shielding without damaging the printed circuit board and/or components thereon, and effectively shield all frequencies up to the highest frequency of operation or concern of the radio frequency device.
The invention overcomes the above-identified problems as well as other shortcomings and deficiencies of existing technologies.
According to one embodiment, the present invention provides a radio frequency shield enclosure having a removable cover. The enclosure includes a frame adapted for attachment to a printed circuit board; and a cover having a plurality of openings, a plurality of grounding finger contacts, and a plurality of alignment finger contacts. The plurality of alignment finger contacts mate with alignment locations on the frame to align the cover therewith, and the plurality of grounding finger contacts electrically connect the cover to the frame. The cover openings and spaces between the plurality of grounding finger contacts and the plurality of alignment finger contacts are less than a wavelength of a frequency of operation and concern.
According to another specific embodiment, the present invention also provides a method of operation for assembling a radio frequency shield enclosure having a removable cover to a printed circuit board. The method includes the steps of fabricating a frame adapted for attachment to a printed circuit board; fabricating a cover having a plurality of openings, a plurality of grounding finger contacts, and a plurality of alignment finger contacts; and assembling the frame and cover together before attaching to the printed circuit board. The plurality of alignment finger contacts mate with alignment locations on the frame to align the cover therewith. The plurality of grounding finger contacts electrically connect the cover to the frame, whereby the cover openings and spaces between the plurality of grounding finger contacts and the plurality of alignment finger contacts are less than a wavelength of a frequency of operation and concern.
Features and advantages of the invention will be apparent from the following description of the embodiments, given for the purpose of disclosure and taken in conjunction with the accompanying drawings.